It appears on Wikipedia alone, there are many different ways to calculate a population of a metropolitan area. If you are looking at city limits alone, Atlanta city proper has fewer residents than Virginia Beach and Mesa, AZ, ranked at #40 in the US. That is eye opening for me- perhaps Atlanta has a lot of pent up demand for city living considering all the business located here- so that is probably good for Midtown/Downtown/Buckhead.
Wikipedia has a few ways to calculate population on surrounding areas, and the link below has Atlanta ranked at #11 as of 2016. If you look at the growth, though, we have twice the rate of growth than boston (who has 1.75 million more residents), and we have 4 times the rate of Philidelphia. We seem to be running neck and neck with Miami, but with global warming and potentially higher taxes to pay for all the flood control for flooding they are having now, that may change. It does not appear we will eclipse anything in Texas.
I put together a small spreadsheet based on these numbers, and assuming the rate of growth between 2010 and 2016 would remain the same for all cities, Atlanta would overtake Phili in 2028 and Boston in 2058, but even at 2100, Miami would have a few hundred more residents than Atlanta. Perhaps land prices would get much more expensive in Miami, changing the current growth rate.
The unexpected big surprise was (I added Chicago later to the spreadsheet), that Atlanta in on track to overtake Chicago by 2058.
Based on this, in 2058, I had the ranking at NYC, LA, WAS, DAL, HOU, SF, MIA, ATL, CHI, BOS, PHI with ATL at #8. I'm sure either the entity that published the study was a lot smarter than I am, or they cherry picked some statistics to make ATL look a lot better than other competing cities.
https://en.wikipedia.org/wiki/Combin...tistical_areas